On the Internet, data is usually exchanged in client/server mode. In doing this, a client, which is usually a program on a data terminal, for example an arithmetic unit of a user, first sets up a connection to a server and then requests data from this server. This may mean that a browser, as the client, requests HTML pages from a server. A procedure of this type, in which data is sent only on request and is therefore “pulled” by the client, is referred to as “pulling.”
The server would theoretically be able to send its information to the client without being requested to do so, i.e., without first receiving a query, which is referred to as “pushing.” However, to date such applications on the Internet have had limited usage, e.g., for so-called instant messaging.
The Open Mobile Alliance organization (OMA, previously WAP Forum) has developed a push protocol family which may be used to send data from an Internet server to a mobile data terminal (MT) in data push mode, thereby enabling the data to be pushed by the Internet server.
According to this method, however, an Internet server, as the push initiator (PI), which initiates a push and therefore dispatches the data, does not send the data directly to the mobile terminal. Via a push proxy gateway (PPG), i.e., a protocol converter for transmitting data, or a gateway, the data is optimally adjusted to an air interface suitable for wireless transmission. The data may be sent and thereby transmitted from the PPG to the mobile data terminal as either an HTTP or a WAP (WSP) message. This procedure is specified in the so-called push-over-the-air protocol (Push OTA) for wireless pushing and thus dispatch of data.
In an optional refinement, using a so-called session initiation push protocol (SIP), which is suitable for setting up multimedia sessions and was specified by the IETF (Internet Engineering Task Force)—an organization which sets standards for the Internet—data of this type may be packaged and sent to the mobile terminal in the form of OTA SIP. This may increase interoperability between at least two different users and thus data-exchanging platforms.
An exemplary flow chart of a data transmission process of this type is illustrated schematically in FIG. 3. An Internet server 50, as the push initiator, first sends a message 52 containing the control data for a specific mobile data terminal 54, for example a mobile phone, via a push access protocol (PAP) to a gateway 56 and signals the fact that this message 52 should be sent to specific data terminal 54. To do this, gateway 56 must contact data terminal 54 via OTA WSP or OTA HTTP, using a push over-the-air protocol 58.
However, mobile communications network operators usually do not allow just any external server to set up a connection to a mobile subscriber from the Internet without being requested to do so. This means that the desired WSP session or a TCP/IP connection must be set up by the mobile data terminal.
To enable a session/connection to be initiated externally in spite of this, the OMA push protocol defines the so-called session initiation request (SIR) and the session initiation application (SIA). SIA is an application that runs in the mobile terminal and enables the PPG to ask the data terminal to open a push session or an active TCP/IP connection for the purpose of transmitting data to the data terminal.
A possible procedure for this purpose is illustrated schematically in FIG. 4. Once an Internet server 60 has initiated a push via a push-over-the-air protocol 62 and sent a corresponding message to a gateway 64, a connection call 66 (SIR) is sent from gateway 64 to data terminal 68 so that the latter sets up a push session or active TCP/IP connection to Internet server 60 via gateway 64, using push-over-the-air protocol 62. A special, relatively simple code is used for the content of the SIR or SIA (for example of the type “application/vnd.wap.sia”), so that the message has a small data scope. A connection call 66 or SIR, for example, may therefore also be transmitted by SMS (text messaging).